Not applicable.
(1). Field of the Invention
The present invention generally relates to a three-dimensional imaging system and in particular, a three-dimensional imaging system that can be used to process sonar data and create a three-dimensional image based on that sonar data.
(2). Description of the Prior Art
Sonar data obtained from forward-looking sonar systems is typically displayed as range-azimuth and range-elevation plots. Range-azimuth and range-elevation plots are plots that relate intensity of objects to their position relative to the nose of the sonar. These displays are often color coded with the color red being used for areas of intense acoustic reflection and blue for areas of little reflection. These displays are extremely useful. However, these displays have several significant disadvantages. One disadvantage is that they cannot simultaneously show both the horizontal and vertical position of an object. Hence, one has to compare their positions and shapes by mentally combining various views of the highlighted objects. Another significant disadvantage is that the plots are usually provided in range-angle space coordinates instead of x-y-z Cartesian coordinates. Thus, range-azimuth and range-elevation plots are often difficult to visualize by humans.
Side-looking sonars, also known as side-scan sonars, also are typically two-dimensional displays in which gray scale level relates to the intensity of the return of the sonar. For example, shadows (regions having low return values) may be portrayed as dark areas and reflections as relatively lighter shaded objects. The stronger the reflection, the lighter the shade in which the object is displayed. The height of each object is determined solely by the shadow cast by the object. Furthermore, the display of this data is most often in the format of a continuous strip showing the outputs of the port and starboard sonar transducers separated by a blanked out region representing the altitude at which the side-scan was traveling above the ocean floor. The continuous strip displays neither provide an indication of the vehicle""s heading nor are they in Cartesian coordinates. The viewer can obtain the side-scan sonar""s position in global coordinates only by reading the latitude-longitude heading data recorded on a separate data channel. However, the global coordinates then have to be converted to Cartesian coordinates.
Various prior art imaging systems used in sonar applications are described in the following documents. Von Ramm et al., U.S. Pat. No. 4,694,434 discloses a three-dimensional imaging system using outputs from a two-dimensional transducer array. Nakamura, U.S. Pat. No 4,815,045 discloses a seabed surveying apparatus in which side-looking sonar data is combined with a multi-beam echo sounder data so that topographic and bathymetric data can be superimposed on a common X-Y coordinate display field. Kosalos et al., U.S. Pat. No. 5,200,931 discloses a volumetric and terrain imaging sonar system for generating a three-dimensional image wherein forward-looking and side-looking sonar data is combined into one image. Fischer, U.S. Pat. No. 5,699,318 discloses a video display system of that is configured to provide a video display of the bottom of a body of water using data collected from a side-looking sonar system. Medeiros, U.S. Pat. No. 5,812,494 describes a system for generating a wide-angle, forward-looking bathymetric map of the region ensonified by a single ping. Wilk, U.S. Pat. No. 6,002,644 discloses an underwater imaging system for surveying underwater topography using arrays of transducers. In one embodiment, the transducers are mounted on the side of a cylindrical body.
It is clear that there has existed a long and unfilled need in the art for a system that can simultaneously display forward-looking sonar data, side-looking sonar data, bathymetry data, bottom/sediment data, and vehicle and target data. The present invention meets this need while avoiding the aforementioned shortcomings of the techniques known in the prior art.
A first object of the invention is provision of sonar data as a three dimensional view.
Another object is the combination of various sonar sources with navigational information in order to provide a three dimensional view.
The present invention is directed to a three-dimensional sonar imaging system that processes forward-looking sonar data, side-looking sonar data, vehicle position and navigation data and renders a three-dimensional image of an ensonified region. The image is based on the processed data and, in one embodiment, comprises the simultaneous display of bathymetry data, bottom or sediment type data, side-scan sonar map data, navigation data, vehicle motion data, water surface data and detection/cluster data. In an alternate embodiment, each one of these data types can be displayed individually.
Thus, in one aspect, the present invention is directed to a method of generating a three-dimension image of a region ensonified by a source of acoustic signals. This includes the step of providing sonar data corresponding to the ensonified region wherein the sonar data include side-looking sonar data, bathymetric sonar data, detection and cluster data, and navigation data and altitude data relating to the position and movement of the source of acoustic signals. The navigation and altitude data is processed so as to format the navigation and altitude data into center-of-scenebounding coordinates. The method also includes processing the detection and cluster data, the bathymetric data, and the side-looking sonar data to produce geometry objects based on each data type. These objects are then rendered into a three-dimensional image comprising the geometry objects. The position of all geometry objects are offset in accordance with the center-of-scenebounding coordinates. The system then displays the rendered three-dimensional image with the objects offset.
In a related aspect, the present invention is directed to a three-dimensional imaging system for use with a sonar system that provides side-looking sonar data, bathymetric data, detection and cluster data, and navigation data and altitude data. The three-dimensional imaging system includes data receiving circuitry, a processor, and a display device. The data receiving circuitry reviews the side-looking sonar data, bathymetric data, detection and cluster data, navigation data, and altitude data. The processor converts the received navigation and altitude data into center-of-scenebounding coordinates, processes the received detection and cluster data, processes the received bathymetric data so as to produce geometry objects, processes the received side-looking sonar data to produce geometry objects, renders a three-dimensional image comprising the geometry objects based on the detection and cluster data, the bathymetric data and the three-dimensional side-looking sonar data, and offsets the position of all geometry objects in accordance with the center-of-scenebounding coordinates. The display device displays the rendered three-dimensional image.